﻿/*
*    Qizx/open 3.0 beta
*
* This code is the open-source version of Qizx.
* Copyright (C) 2004-2009 Axyana Software -- All rights reserved.
*
* The contents of this file are subject to the Mozilla Public License 
*  Version 1.1 (the "License"); you may not use this file except in 
*  compliance with the License. You may obtain a copy of the License at
*  http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
*  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
*  for the specific language governing rights and limitations under the
*  License.
*
* The Initial Developer of the Original Code is Xavier Franc - Axyana Software.
*
*/
using System;
using EvaluationException = System.Qizx.Api.EvaluationException;
using XMLPushStreamBase = System.Qizx.Xdm.XMLPushStreamBase;
using System.Qizx.XQuery;
using ArraySequence = System.Qizx.XQuery.Dt.ArraySequence;
using ErrorValue = System.Qizx.XQuery.Impl.ErrorValue;

namespace System.Qizx.XQuery.Op {
    class WhileExpr : Expression {
        public Expression cond;
        public Expression block;

        public WhileExpr(Expression cond, Expression block) {
            this.cond = cond;
            this.block = block;
        }

        public void dump(ExprDisplay d) {
            d.header(this);
            d.child(cond);
            d.child(block);
        }

        public override Expression Child(int rank) {
            switch (rank) {
                case 0:
                    return cond;
                case 1:
                    return block;
            }
            return null;
        }

        public Expression staticCheck(ModuleContext context, int flags) {
            cond = context.staticCheck(cond, 0);
            block = context.simpleStaticCheck(block, 0);
            // TODO
            return this;
        }

        public override bool isVacuous() {
            return UpdatingExpr.isVacuous(block);
        }

        public int getFlags() {
            return UpdatingExpr.isUpdating(block) ? UPDATING : 0;
        }

        public override XQValue eval(Focus focus, EvalContext context) {
            context.at(this);
            while (cond.evalEffectiveBooleanValue(focus, context)) {
                block.eval(focus, context);
            }
            return XQValues.Empty;
        }
    }
}